The need for methods to detect small molecule analytes in small quantities has motivated the development of a variety of biosensing techniques. For example, current high sensitivity immunoassay techniques use a competitive assay reaction scheme that requires washing between sample addition and analyte detection to remove background signal and provide required sensitivity. This washing adds additional steps and complexity to the technique, limiting its use. There remains a need for biosensing techniques with very high sensitivity that are simple enough to be suitable for point of care applications.